Team 2928 pre season


#1

We have been able to create a new design will half the bolts but still retain the idea of a speedy brick. The weight has gone down drastically and we have changed some things around from robots in years past. I believe this is our best one yet.we will release it bit by bit. but you can gather some things from this image. hope you enjoy. if you have any questions ask, but they might get answered in due time.https://www.instagram.com/p/Bqv64jlFtj1/?utm_source=ig_web_copy_link


#2

Is that 1/4" polycarbonate?


#3

Yes, we used 1/4" because it fits inside of the rev extrusion.


#4

Yo that’s p neat so need to use screws or anything once you place it in?


#5

We did not have to use and screws to hold the polycarb in because it is sandwiched between multiple rev pieces, or the rev and the aluminium. non of it has the chance of falling out unless you take the robot apart.


#6

Oof that is fast, how do you justify going that quick while still being able to drive it?


#7

so we do not really have a reason for going that fast besides we could. we have never done a fully custom drive train, and since this was our very first attempt at making a custom gearbox, we thought why not go big or go home. we can change it around in we want, but we thought that it would be really fun to make a robot that could do this. it was also a chance for our team to experiment and see what we were capable of since it was our first time and all. hope this answers your question.


#8

Fair enough, let us know how it was to drive/control. I’m curious how much of that top end speed could actually be used or if it will be twitchy beyond control. Cool design!


#9

I personally love it when it drives, but i am not the best authority. i asked our driver, and this is what he said.
First impression, it’s extremely responsive and very fast. It’s a lot of fun to drive and you basically teleport around the field. You want to turn 180? Bam half a second turn. Want to drive across? Blink and it’s there. It does require a lot of focus to drive since it’s so fast and isn’t very noobie friendly. If I was given this drive train for competition, I’d take it in an instant.
But i do think that it can be a bit slippy at times due to its speed and its wheels. we changed them, so its a bit slippy. so i would say its a bit rowdy and would definitely need a trained hand to just start learning to use it.


#10

Do you have videos of it driving?


#11

On Friday we’ll have the shop, so I can get some footage of me driving. That being said, we do have this…

Note, I only had one talon on each side working in that video, the robot spins much faster than that. (We also strapped in the radio :D)


#12

Do you have any weights on it to get it close to competition speed? By the time that you get to 26 fps I would assume that you could accelerate too slowly for it to be effective on an frc scale.


#13

we were able to test it’s torque by placing 60 lb worth of batteries on it to get a goof gauge of its pulling power. we have not tried a speed test with the weight thought. i don’t think the batteries would stay on at that speed. And like jett said, we will had the shop on Friday, so we can tests stuff out then. well keep you updated


#14

everyone keeps mentioning how its fast but im not seeing a video. am i missing it? or are we just guessing by gear ratio?


#15

Hey, I’m a mentor on 2928 that has been working with the design/mechanical students on this off season project. We completed the assembly, wiring, and programming right before the school winter break, so actual drive time with the new drivetrain has been pretty minimal so far. I’ll be in with them later today and try to get a video of it driving in high gear (without hitting the walls in the hallway, Jett!).

As Julius has mentioned, this isn’t necessarily a design that we would use in competition, but we wanted to try out a few design ideas when we had time to rework and explore, mainly:

  • Using .236" polycarbonate plates inside the channels of REV extrusion for lateral rigidity and support, allowing fewer fasteners and a slide together assembly
  • Moving from .250" and .190" 6061 plates on our drivetrain (which is a lot of material!) to .160" 7075 plates using better weight reduction (driven by structural analysis)
  • Designing our own shifting gearboxes (still using the Vex ball shifter core), which the team has done in the past (but it’s been 5+ years, so this was new to the current students), including flipping the CIMs over the wheels so we can mount the battery low and centered in the robot (low center of gravity is generally agreed to be a good thing)
  • Creating a base drivetrain that we can customize and quickly attach prototypes.
  • Miscellaneous other ideas, that are new to us, but not so much to other teams. Thing’s we’ve wanted to try (or get better at) include: a more serviceable robot through reduction of fasteners for removing the sides (belt replacement, wheel swapping, etc.), elimination of all axel spacers (my favorite!) through the use of snap rings and e-clips, templated panels (e.g. belly pan CAD outlines that can be given to the electrical and other sub teams for layout work early in the design process), different battery mounting (AndyMark am-0477), part numbers for our drawings and manufactured parts! (revolutionary, I know), switching over to the NITRA pneumatics components from Automation Direct, etc. etc.

Results (so far):

  • The .160" 7075 plate, with REV extrusion, and .236" polycarbonate plates has proven to be very rigid (.125 center drop on our west coast drivetrain has almost no flex when applying downward force on diagonally opposing corners)
  • Assembly was very smooth and required almost no rework or adjustments (we took notes, so I hope we can delete that ‘almost’ from our build season)
  • Not a single shaft collar or spacer on the robot! (no more frantically searching the pit for the runaway spacers!)
  • 3 CIM gearbox can easily be adjusted to be a 2 CIM or 1 CIM gearbox (I’m sure you can figure that one out), but can also be used to test with mini CIMs or the magical NEOs (any motor that has a nonexistent data sheet has the potential to be completely full of magic)
  • The spacing of our driving axel and shifting driven axel allows for 5 different gearing options for both high and low gear (12t motor pinion gears drive a 72t in the first reduction, allowing us to swap out both the high and low driving gear), which in the current configuration result in options for 3.40:1 (current high)
    , 5.28:1, 6.82:1, 8.10:1, and 10.59:1 (current low). Using the formulas from the JVN spreadsheet over at Vex, this gives us a top (free) speed of 27.36 ft/s and using a 81% real life speed loss constant an expected real life speed of 22.16 ft/s in the current configuration (Julius, I think the 26 ft/s is with the 14t pinions and a 70t driven gear in the first reduction, with a 2.83:1 total reduction, a free speed of 32.83 ft/s, and real life speed that is calculated at 26.59 ft/s).
  • The NITRA pneumatics gages, regulator, etc. are wonderful! (as I’m sure many of you already know… Think we’re late to joining that party…)
  • The battery mount (am-0477) looks to simple to be effective, compared to the battery boxes that be usually build, but I have to say I’m really impressed with how well it works (simple is an amazing design goal!)

Does anyone have any easy tricks (e.g. iphone apps, or code snippets to give the programming team) that can accurately (semi-accurately) measure real world speeds? The look of shock and excitement on our driver’s face is slightly less than scientific in approach… but it goes to 11…

More to come!

-Brent


#16

I think there was more in the post before, but the Instagram post has the hashtag “#26FPS”.


#17

Woww :fire::fire::fire::fire: mechanical is so cool​:telescope::heart_eyes::heart_eyes::heart_eyes::fire::fire::fire::star_struck:


#18

@Julius-Team2928

any luck getting the video up from last Friday? Sure, Chief Delphi was down for upgrades since then, but it’s been up for hour (maybe plural) now…